Palladium-Induced Intramolecular Coupling Reactions of Some Alkenyl(o-iodobenzyl)silanes

The first examples for the formation of siloles by intramolecular Heck-type cyclizations are reported. Upon treatment with [PdCl₂(PPh₃)], the (o-iodobenzyl)vinylsilanes 4a and 4c give the siloles 5a and 5c as well as the vinyl-transfer products 6a and 6c (Scheme 2), respectively. Under CO pressure 4a and 4c react to the carbonylation products in modest yields (Scheme 3). In addition, carbonylative crossover is observed with 4a .     

A Model for the Cobalamin-Dependent Methionine Synthase

The acid-catalyzed transfer of a Me group from N,N-dimethylaniline ( 6 ) to vitamin-B₁₂-derived Co^I complexes 2a , b was realized (Scheme 3). Hexane-1-thiol ( 8 ) was methylated by the methylcobalt complexes 4a , b in the presence of pyridine. Conditions for the complete cycle, i.e., Me transfer from 6 to 8 with Co^I complexes acting as a nucleophile and a nucleofuge have been established. The importance of Zn²⁺ as activating agent and of the basicity of tertiary amines for the Me transfer has been investigated.     

Further numerical methods for the Falkner-Skan equations: Shooting and continuation techniques

We consider in this paper the numerical solution of the Falkner-Skan differential equation, modelling under some similarity assumptions the boundary layer equation. We look for the extremal solution of this third order differential equation. The methods we use are basically the Newton method with a shooting process, which is coupled with a continuation method: they allow us to follow the solution arcs which contain regular and turning point solutions.     

Polycyclopentane Als Steroid-Analoga

Polycyclopentanes as Steroid Analoga The synthesis of linearly annellated pentaquinanes from a readily available triquinane is reported.